Methods and system for operating a driveline

ABSTRACT

Systems and methods for operating a driveline of a hybrid vehicle are described. In one example, a torque that is produced by an engine is adjusted responsive to a transmission oil temperature and a speed of a torque converter impeller so that temperature of oil in a transmission lube circuit may be maintained at a desired temperature.

FIELD

The present description relates to methods and a system for operating adriveline of a hybrid vehicle.

BACKGROUND AND SUMMARY

A hybrid vehicle may include an internal combustion engine and anelectric machine to provide propulsive effort. The internal combustionengine may be deactivated and stopped during low demand conditions toconserve fuel. The electric machine may provide propulsive effort at lowand high demand conditions to conserve fuel and increase drivelineoutput. The internal combustion engine and the driveline disconnectclutch may be selectively decoupled from each other via a drivelinedisconnect clutch. The driveline disconnect clutch may closed when theinternal combustion engine is providing power to the electric machine tocharge an electric energy storage device. However, charging an electricenergy storage device may lead to higher transmission oil temperatureswhen the hybrid vehicle is not moving since a transmission oil pump'sflow rate may be limited. In particular, transmission oil may bedirected to the driveline disconnect clutch instead of a transmissionoil cooler so that the driveline disconnect clutch does not slip and sothat charging of the electric energy storage device may be maintained.The higher transmission oil temperatures may cause accelerateddegradation of transmission oil and its lubricating properties.

The inventors herein have recognized the above-mentioned issues and havedeveloped a driveline operating method, comprising: adjusting enginetorque responsive to a transmission oil temperature and a speed of atorque converter impeller via a controller; and adjusting a transmissionline pressure responsive to the engine torque.

By adjusting engine torque responsive to a transmission oil temperatureand a speed of a torque converter impeller, it may be possible toprovide the technical result of limiting transmission oil temperatureduring conditions when transmission oil pump flow may be constrained.Further, engine torque may be adjusted to a level that provides asignificant portion of torque to provide a desired level of electricenergy storage device charging while slippage of a driveline disconnectmay be reduced. In one example, transmission line pressure may beadjusted so that driveline disconnect clutch torque capacity follows thereduction in engine torque so that oil flow to the transmission oilcooler may be improved, thereby limiting transmission oil temperaturewhile delivering charge to an electric energy storage device.

The present description may provide several advantages. In particular,the approach may reduce transmission oil temperatures and degradation.Further, the approach may allow continued charging of an electric energystorage device. In addition, the approach may compensate for conditionswhen a torque converter clutch is open or locked so that cooling oftransmission oil may be permitted.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an embodiment, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings, where:

FIG. 1 is a schematic diagram of an engine;

FIG. 2 is a schematic diagram of a hybrid vehicle driveline;

FIG. 3 shows a block diagram for controlling transmission oiltemperature;

FIG. 4 shows an example driveline operating sequence;

FIG. 5 shows example transmission oil line circuitry;

FIG. 6A shows an example plot that illustrates a priority zone fortransmission oil pressure control;

FIG. 6B shows an example table for limiting torque converter impellertorque; and

FIG. 7 shows a method for operating a driveline that includes an engineand an ISG.

DETAILED DESCRIPTION

The present description is related to operating a driveline of a hybridvehicle. The driveline may include an engine of the type shown inFIG. 1. The hybrid driveline may be configures as shown in FIG. 2. Thehybrid vehicle driveline may be operated via a controller as shown inFIG. 3. The hybrid driveline may be operated as shown in the sequence ofFIG. 4. The hybrid driveline may include transmission hydrauliccircuitry as shown in FIG. 5. Pressure with the transmission may beadjusted according to a priority zone as shown in FIG. 6A. Torqueconverter impeller torque may be limited via a table as shown in FIG.6B. The driveline may be operated according to the method of FIG. 7.

Referring to FIG. 1, internal combustion engine 10, comprising aplurality of cylinders, one cylinder of which is shown in FIG. 1, iscontrolled by electronic engine controller 12. The controller 12receives signals from the various sensors shown in FIGS. 1 and 2 andemploys the actuators shown in FIGS. 1 and 2 to adjust engine anddriveline operation based on the received signals and instructionsstored in memory of controller 12.

Engine 10 is comprised of cylinder head 35 and block 33, which includecombustion chamber 30 and cylinder walls 32. Piston 36 is positionedtherein and reciprocates via a connection to crankshaft 40. Flywheel 97and ring gear 99 are coupled to crankshaft 40. Optional starter 96(e.g., low voltage (operated with less than 30 volts) electric machine)includes pinion shaft 98 and pinion gear 95. Pinion shaft 98 mayselectively advance pinion gear 95 to engage ring gear 99. Starter 96may be directly mounted to the front of the engine or the rear of theengine. In some examples, starter 96 may selectively supply power tocrankshaft 40 via a belt or chain. In one example, starter 96 is in abase state when not engaged to the engine crankshaft. Combustion chamber30 is shown communicating with intake manifold 44 and exhaust manifold48 via respective intake valve 52 and exhaust valve 54. Each intake andexhaust valve may be operated by an intake cam 51 and an exhaust cam 53.The position of intake cam 51 may be determined by intake cam sensor 55.The position of exhaust cam 53 may be determined by exhaust cam sensor57. Intake valve 52 may be selectively activated and deactivated byvalve activation device 59. Exhaust valve 54 may be selectivelyactivated and deactivated by valve activation device 58. Valveactivation devices 58 and 59 may be electro-mechanical devices.

Direct fuel injector 66 is shown positioned to inject fuel directly intocylinder 30, which is known to those skilled in the art as directinjection. Port fuel injector 67 is shown positioned to inject fuel intothe intake port of cylinder 30, which is known to those skilled in theart as port injection. Fuel injectors 66 and 67 deliver liquid fuel inproportion to pulse widths provided by controller 12. Fuel is deliveredto fuel injectors 66 and 67 by a fuel system (not shown) including afuel tank, fuel pump, and fuel rail (not shown).

In addition, intake manifold 44 is shown communicating with turbochargercompressor 162 and engine air intake 42. In other examples, compressor162 may be a supercharger compressor. Shaft 161 mechanically couplesturbocharger turbine 164 to turbocharger compressor 162. Optionalelectronic throttle 62 adjusts a position of throttle plate 64 tocontrol air flow from compressor 162 to intake manifold 44. Pressure inboost chamber 45 may be referred to a throttle inlet pressure since theinlet of throttle 62 is within boost chamber 45. The throttle outlet isin intake manifold 44. In some examples, throttle 62 and throttle plate64 may be positioned between intake valve 52 and intake manifold 44 suchthat throttle 62 is a port throttle. Compressor recirculation valve 47may be selectively adjusted to a plurality of positions between fullyopen and fully closed. Waste gate 163 may be adjusted via controller 12to allow exhaust gases to selectively bypass turbine 164 to control thespeed of compressor 162. Air filter 43 cleans air entering engine airintake 42.

Distributorless ignition system 88 provides an ignition spark tocombustion chamber 30 via spark plug 92 in response to controller 12.Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled toexhaust manifold 48 upstream of three-way catalyst 70. Alternatively, atwo-state exhaust gas oxygen sensor may be substituted for UEGO sensor126.

Catalyst 70 can include multiple bricks. In another example, multipleemission control devices, each with multiple bricks, can be used.

Controller 12 is shown in FIG. 1 as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, read-onlymemory 106 (e.g., non-transitory memory), random access memory 108, keepalive memory 110, and a conventional data bus. Controller 12 is shownreceiving various signals from sensors coupled to engine 10, in additionto those signals previously discussed, including: engine coolanttemperature (ECT) from temperature sensor 112 coupled to cooling sleeve114; a position sensor 134 coupled to an accelerator pedal 130 (e.g., ahuman/machine interface) for sensing force applied by human driver 132;a position sensor 154 coupled to brake pedal 150 (e.g., a human/machineinterface) for sensing force applied by human driver 132, a measurementof engine manifold pressure (MAP) from pressure sensor 122 coupled tointake manifold 44; an engine position sensor from a Hall effect sensor118 sensing crankshaft 40 position; a measurement of air mass enteringthe engine from sensor 120; and a measurement of throttle position fromsensor 68. Barometric pressure may also be sensed (sensor not shown) forprocessing by controller 12. In a preferred aspect of the presentdescription, engine position sensor 118 produces a predetermined numberof equally spaced pulses every revolution of the crankshaft from whichengine speed (RPM) can be determined.

Controller 12 may also receive input from human/machine interface 11. Arequest to start the engine or vehicle may be generated via a human andinput to the human/machine interface 11. The human/machine interface 11may be a touch screen display, pushbutton, key switch or other knowndevice.

During operation, each cylinder within engine 10 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. During the intake stroke,generally, the exhaust valve 54 closes and intake valve 52 opens. Air isintroduced into combustion chamber 30 via intake manifold 44, and piston36 moves to the bottom of the cylinder so as to increase the volumewithin combustion chamber 30. The position at which piston 36 is nearthe bottom of the cylinder and at the end of its stroke (e.g. whencombustion chamber 30 is at its largest volume) is typically referred toby those of skill in the art as bottom dead center (BDC).

During the compression stroke, intake valve 52 and exhaust valve 54 areclosed. Piston 36 moves toward the cylinder head so as to compress theair within combustion chamber 30. The point at which piston 36 is at theend of its stroke and closest to the cylinder head (e.g. when combustionchamber 30 is at its smallest volume) is typically referred to by thoseof skill in the art as top dead center (TDC). In a process hereinafterreferred to as injection, fuel is introduced into the combustionchamber. In a process hereinafter referred to as ignition, the injectedfuel is ignited by known ignition means such as spark plug 92, resultingin combustion.

During the expansion stroke, the expanding gases push piston 36 back toBDC. Crankshaft 40 converts piston movement into a rotational power ofthe rotary shaft. Finally, during the exhaust stroke, the exhaust valve54 opens to release the combusted air-fuel mixture to exhaust manifold48 and the piston returns to TDC. Note that the above is shown merely asan example, and that intake and exhaust valve opening and/or closingtimings may vary, such as to provide positive or negative valve overlap,late intake valve closing, or various other examples.

FIG. 2 is a block diagram of a vehicle 225 including a powertrain ordriveline 200. The powertrain of FIG. 2 includes engine 10 shown inFIG. 1. Powertrain 200 is shown including vehicle system controller 255,engine controller 12, electric machine controller 252, transmissioncontroller 254, and energy storage device controller 253. Thecontrollers may communicate over controller area network (CAN) 299. Eachof the controllers may provide information to other controllers such aspower output limits (e.g., power output of the device or component beingcontrolled not to be exceeded), power input limits (e.g., power input ofthe device or component being controlled not to be exceeded), poweroutput of the device being controlled, sensor and actuator data,diagnostic information (e.g., information regarding a degradedtransmission, information regarding a degraded engine, informationregarding a degraded electric machine, information regarding degradedbrakes). Further, the vehicle system controller 255 may provide commandsto engine controller 12, electric machine controller 252, andtransmission controller 254 to achieve driver input requests and otherrequests that are based on vehicle operating conditions.

For example, in response to a driver releasing an accelerator pedal andvehicle speed, vehicle system controller 255 may request a desired wheelpower or a wheel power level to provide a desired rate of vehicledeceleration. The requested desired wheel power may be provided byvehicle system controller 255 requesting a first braking power fromelectric machine controller 252 and a second braking power from enginecontroller 212, the first and second powers providing a desireddriveline braking power at vehicle wheels 216.

In other examples, the partitioning of controlling powertrain devicesmay be partitioned differently than is shown in FIG. 2. For example, asingle controller may take the place of vehicle system controller 255,engine controller 12, electric machine controller 252, and transmissioncontroller 254. Alternatively, the vehicle system controller 255 and theengine controller 12 may be a single unit while the electric machinecontroller 252, and the transmission controller 254 are standalonecontrollers.

In this example, powertrain 200 may be powered by engine 10 and electricmachine 240. In other examples, engine 10 may be omitted. Engine 10 maybe started with an engine starting system shown in FIG. 1, via BISG 219,or via driveline integrated starter/generator (ISG) 240 also known as anintegrated starter/generator. A speed of BISG 219 may be determined viaoptional BISG speed sensor 203. Driveline ISG 240 (e.g., high voltage(operated with greater than 30 volts) electrical machine) may also bereferred to as an electric machine, motor, and/or generator. Further,power of engine 10 may be adjusted via power actuator 204, such as afuel injector, throttle, etc.

BISG is mechanically coupled to engine 10 via belt 231. BISG may becoupled to crankshaft 40 or a camshaft (e.g., 51 or 53 of FIG. 1). BISGmay operate as a motor when supplied with electrical power via electricenergy storage device 275 or low voltage battery 280. BISG may operateas a generator supplying electrical power to electric energy storagedevice 275 or low voltage battery 280. Bi-directional DC/DC converter281 may transfer electrical energy from a high voltage buss 274 to a lowvoltage buss 273 or vice-versa. Low voltage battery 280 is electricallycoupled to low voltage buss 273. Electric energy storage device 275 iselectrically coupled to high voltage buss 274. Low voltage battery 280selectively supplies electrical energy to starter motor 96.

An engine output power may be transmitted to an input or first side ofpowertrain disconnect clutch 235 through dual mass flywheel 215.Disconnect clutch 236 may be electrically or hydraulically actuated. Thedownstream or second side 234 of disconnect clutch 236 is shownmechanically coupled to ISG input shaft 237.

ISG 240 may be operated to provide power to powertrain 200 or to convertpowertrain power into electrical energy to be stored in electric energystorage device 275 in a regeneration mode. ISG 240 is in electricalcommunication with inverter 276, and inverter 276 is in electricalcommunication with energy storage device 275. Inverter 276 may convertdirect current (DC) power from electric energy storage device intoalternating current (AC) power to operate ISG 240 as a motor.Alternatively, inverter 276 may convert AC power from ISG 240 into DCpower to store in electric energy storage device 275. ISG 240 has ahigher output power capacity than starter 96 shown in FIG. 1 or BISG219. Further, ISG 240 directly drives powertrain 200 or is directlydriven by powertrain 200. There are no belts, gears, or chains to coupleISG 240 to powertrain 200. Rather, ISG 240 rotates at the same rate aspowertrain 200. Electrical energy storage device 275 (e.g., high voltagebattery or power source) may be a battery, capacitor, or inductor. Thedownstream side of ISG 240 is mechanically coupled to the impeller 285of torque converter 206 via shaft 241. The upstream side of the ISG 240is mechanically coupled to the disconnect clutch 236. ISG 240 mayprovide a positive power or a negative power to powertrain 200 viaoperating as a motor or generator as instructed by electric machinecontroller 252.

Torque converter 206 includes a turbine 286 to output power to inputshaft 270. Input shaft 270 mechanically couples torque converter 206 toautomatic transmission 208. Torque converter 206 also includes a torqueconverter bypass lock-up clutch 212 (TCC). Power is directly transferredfrom impeller 285 to turbine 286 when TCC is locked. TCC is electricallyoperated by controller 12. Alternatively, TCC may be hydraulicallylocked. In one example, the torque converter may be referred to as acomponent of the transmission.

When torque converter lock-up clutch 212 is fully disengaged, torqueconverter 206 transmits engine power to automatic transmission 208 viafluid transfer between the torque converter turbine 286 and torqueconverter impeller 285, thereby enabling power multiplication. Incontrast, when torque converter lock-up clutch 212 is fully engaged, theengine output power is directly transferred via the torque converterclutch to an input shaft 270 of transmission 208. Alternatively, thetorque converter lock-up clutch 212 may be partially engaged, therebyenabling the amount of power directly relayed to the transmission to beadjusted. The transmission controller 254 may be configured to adjustthe amount of power transmitted by torque converter 212 by adjusting thetorque converter lock-up clutch in response to various engine operatingconditions, or based on a driver-based engine operation request.

Torque converter 206 also includes pump 283 that pressurizes fluid tooperate disconnect clutch 236, forward clutch 210, and gear clutches211. Pump 283 is driven via impeller 285, which rotates at a same speedas ISG 240.

Automatic transmission 208 includes gear clutches (e.g., gears 1-10) 211and forward clutch 210. Automatic transmission 208 is a fixed ratiotransmission. Alternatively, transmission 208 may be a continuouslyvariable transmission that has a capability of simulating a fixed gearratio transmission and fixed gear ratios. The gear clutches 211 and theforward clutch 210 may be selectively engaged to change a ratio of anactual total number of turns of input shaft 270 to an actual totalnumber of turns of wheels 216. Gear clutches 211 may be engaged ordisengaged via adjusting fluid supplied to the clutches via shiftcontrol solenoid valves 209. Power output from the automatictransmission 208 may also be relayed to wheels 216 to propel the vehiclevia output shaft 260. Specifically, automatic transmission 208 maytransfer an input driving power at the input shaft 270 responsive to avehicle traveling condition before transmitting an output driving powerto the wheels 216. Transmission controller 254 selectively activates orengages TCC 212, gear clutches 211, and forward clutch 210. Transmissioncontroller also selectively deactivates or disengages TCC 212, gearclutches 211, and forward clutch 210. Output of transmission 208 issupplied to wheels 216.

In response to a request to accelerate vehicle 225, vehicle systemcontroller may obtain a driver demand power or power request from anaccelerator pedal or other device. Vehicle system controller 255 thenallocates a fraction of the requested driver demand power to the engineand the remaining fraction to the ISG or BISG. Vehicle system controller255 requests the engine power from engine controller 12 and the ISGpower from electric machine controller 252. If the ISG power plus theengine power is less than a transmission input power limit (e.g., athreshold value not to be exceeded), the power is delivered to torqueconverter 206 which then relays at least a fraction of the requestedpower to transmission input shaft 270. Transmission controller 254selectively locks torque converter clutch 212 and engages gears via gearclutches 211 in response to shift schedules and TCC lockup schedulesthat may be based on input shaft power and vehicle speed. In someconditions when it may be desired to charge electric energy storagedevice 275, a charging power (e.g., a negative ISG power) may berequested while a non-zero driver demand power is present. Vehiclesystem controller 255 may request increased engine power to overcome thecharging power to meet the driver demand power.

In response to a request to decelerate vehicle 225 and provideregenerative braking, vehicle system controller may provide a negativedesired wheel power (e.g., desired or requested powertrain wheel power)based on vehicle speed and brake pedal position. Vehicle systemcontroller 255 then allocates a fraction of the negative desired wheelpower to the ISG 240 and the engine 10. Vehicle system controller mayalso allocate a portion of the requested braking power to frictionbrakes (not shown). Further, vehicle system controller may notifytransmission controller 254 that the vehicle is in regenerative brakingmode so that transmission controller 254 shifts gears 211 based on aunique shifting schedule to increase regeneration efficiency. Engine 10and ISG 240 may supply a negative power to transmission input shaft 270,but negative power provided by ISG 240 and engine 10 may be limited bytransmission controller 254 which outputs a transmission input shaftnegative power limit (e.g., not to be exceeded threshold value).Further, negative power of ISG 240 may be limited (e.g., constrained toless than a threshold negative threshold power) based on operatingconditions of electric energy storage device 275, by vehicle systemcontroller 255, or electric machine controller 252. Any portion ofdesired negative wheel power that may not be provided by ISG 240 becauseof transmission or ISG limits may be allocated to engine 10 and/orfriction brakes (not shown) so that the desired wheel power is providedby a combination of negative power (e.g., power absorbed) via frictionbrakes (not shown), engine 10, and ISG 240.

Accordingly, power control of the various powertrain components may besupervised by vehicle system controller 255 with local power control forthe engine 10, transmission 208, and electric machine 240 provided viaengine controller 12, electric machine controller 252, and transmissioncontroller 254.

As one example, an engine power output may be controlled by adjusting acombination of spark timing, fuel pulse width, fuel pulse timing, and/orair charge, by controlling throttle opening and/or valve timing, valvelift and boost for turbo- or super-charged engines. In the case of adiesel engine, controller 12 may control the engine power output bycontrolling a combination of fuel pulse width, fuel pulse timing, andair charge. Engine braking power or negative engine power may beprovided by rotating the engine with the engine generating power that isinsufficient to rotate the engine. Thus, the engine may generate abraking power via operating at a low power while combusting fuel, withone or more cylinders deactivated (e.g., not combusting fuel), or withall cylinders deactivated and while rotating the engine. The amount ofengine braking power may be adjusted via adjusting engine valve timing.Engine valve timing may be adjusted to increase or decrease enginecompression work. Further, engine valve timing may be adjusted toincrease or decrease engine expansion work. In all cases, engine controlmay be performed on a cylinder-by-cylinder basis to control the enginepower output.

Electric machine controller 252 may control power output and electricalenergy production from ISG 240 by adjusting current flowing to and fromfield and/or armature windings of ISG as is known in the art.

Transmission controller 254 receives transmission input shaft positionvia position sensor 271. Transmission controller 254 may converttransmission input shaft position into input shaft speed viadifferentiating a signal from position sensor 271 or counting a numberof known angular distance pulses over a predetermined time interval.Transmission controller 254 may receive transmission output shaft torquefrom torque sensor 272. Alternatively, sensor 272 may be a positionsensor or torque and position sensors. If sensor 272 is a positionsensor, controller 254 may count shaft position pulses over apredetermined time interval to determine transmission output shaftvelocity. Transmission controller 254 may also differentiatetransmission output shaft velocity to determine transmission outputshaft acceleration. Transmission controller 254, engine controller 12,and vehicle system controller 255, may also receive additiontransmission information from sensors 277, which may include but are notlimited to pump output line pressure sensors, transmission hydraulicpressure sensors (e.g., gear clutch fluid pressure sensors), ISGtemperature sensors, and BISG temperatures, gear shift lever sensors,and ambient temperature sensors. Transmission controller 254 may alsoreceive requested gear input from gear shift selector 290 (e.g., ahuman/machine interface device). Gear shift lever may include positionsfor gears 1-N (where N is the an upper gear number), D (drive), and P(park)

Referring now to FIG. 3, a block diagram of an example drivelinecontroller is shown. The controller described in block diagram 300 maybe included in the method of FIG. 7 and the system of FIGS. 1 and 2 asexecutable instructions stored in non-transitory memory.

Driver demand power, battery state of charge (SOC), and vehicle electricpower consumption are input to torque arbitration block 302. The driverdemand power may be determined via a function that includes empiricallydetermined driver demand power levels is referenced or indexed viaaccelerator pedal position and vehicle speed. Torque arbitration block302 requests engine torque and electric machine torque to meet thedriver demand power, vehicle electric power consumption, and electricenergy storage device charging. Torque arbitration block 302 may requestpositive torque, no torque, or negative torque from the electric machine(e.g., 240 of FIG. 2). Torque arbitration block 302 may request positivetorque (e.g., torque to rotate the driveline) via the electric machinewhen the electric machine is propelling the vehicle. Torque arbitrationblock 302 may request negative torque via the electric machine toprovide charge to the electric energy storage device (e.g., 245 of FIG.2). Torque arbitration block may also request positive torque ornegative torque (e.g. torque extracted from the driveline) from theengine (e.g., 10 of FIG. 1). Negative torque may be provided by ceasingto supply fuel and spark to the engine while the engine is rotated viathe driveline. The engine torque request may be a function of driverdemand power and an amount of power to charge the electric energystorage device. The engine torque request is output from block 302 totorque converter impeller limiting torque block 304. The electricmachine torque request is also output from block 302 to torque converterimpeller limiting torque block 304.

The combined engine torque request and electric machine request arelimited at block 304, thereby limiting the torque converter impellerinput torque. In particular, the sum of the engine torque request andthe electric machine torque request is prevented from exceeding athreshold torque at block 304. The threshold torque may be determinedvia referencing a table or function of empirically determined thresholdtorque values via torque converter impeller speed (e.g., as shown inFIG. 6B), which is equal to ISG speed, which is equal to engine speedwhen the driveline disconnect clutch is fully closed. The table orfunction included in block 304 is also shown being referenced viatransmission oil temperature. Block 304 outputs the limited enginetorque request to blocks 308 and 310. Block 304 may also output alimited electric machine torque request to block 276.

At block 308, an engine torque actuator (e.g., throttle, ignitionsystem, camshaft, valve actuator, etc.) is adjusted to adjust torque ofengine 10. The engine torque is adjusted to provide the limited enginetorque that is output from block 304.

At block 310, a driveline disconnect pressure control valve 310 isadjusted to provide a driveline disconnect clutch torque capacity (e.g.,an amount of torque the driveline disconnect clutch may transfer withoutslipping) that is equal to the limited engine torque plus an offsettorque to ensure that the driveline disconnect clutch 236 remains closedif it is commanded closed. For example, if the requested limited enginetorque is 200 Newton-meters (Nm) and the offset torque is 10 Nm, thenthe torque capacity of the driveline disconnect clutch is adjusted to210 Nm via adjusting a pressure of oil that is supplied to close thedriveline disconnect clutch 236.

The requested electric machine torque is converted into adjustments toinverter 276 so that electric machine 240 provides the requestedpositive or negative torque. For example, switching transistors ofinverter 276 are adjusted to supply AC power to electric machine 240, orthe switching transistors of inverter 276 are adjusted to convert ACpower from electric machine to DC power for storage in electric energystorage device 275 shown in FIG. 2.

The limited engine torque is added to the electric machine torque atelectric machine 285. The combined engine torque and electric machinetorque are input to the torque converter impeller 285. The speed of thetorque converter impeller is returned to limit the torque converterimpeller limiting block 304.

Referring now to FIG. 4, example plots of an engine operating sequenceare shown. The operating sequence may be performed via the system ofFIGS. 1 and 2 in cooperation with the method of FIG. 7. Vertical linesat times t0-t2 represent times of interest during the sequence. Theplots in FIG. 4 are time aligned and occur at the same time.

The first plot from the top of FIG. 4 is a plot of transmission oiltemperature versus time. The vertical axis represents transmission oiltemperature and transmission oil temperature increases in the directionof the vertical axis arrow. The horizontal axis represents time and timeincreases from the left side of the figure to the right side of thefigure. Solid line 402 represents transmission oil temperature. Line 450represents a threshold transmission oil temperature (e.g., a temperaturethat transmission oil temperature is not desired to exceed).

The second plot from the top of FIG. 4 is a plot of engine torque versustime. The vertical axis represents an amount of engine torque that isgenerated and delivered to the driveline. The engine torque increases inthe direction of the vertical axis arrow. The horizontal axis representstime and time increases from the left side of the figure to the rightside of the figure. Solid line 404 represents an amount of enginetorque.

The third plot from the top of FIG. 4 is a plot of electric machinetorque versus time. The vertical axis represents an amount of electricmachine torque that is generated and delivered to the driveline. Thehorizontal axis represents time and time increases from the left side ofthe figure to the right side of the figure. Solid line 406 represents anamount of electric machine torque. The electric machine torque ispositive (e.g., rotating the driveline) when trace 406 is above thehorizontal axis. The positive torque increases in the direction of theup pointing axis arrow. The electric machine torque is negative (e.g.,generating electrical charge) when trace 406 is below the horizontalaxis. The magnitude of the negative torque increases in the direction ofthe down pointing axis arrow.

The fourth plot from the top of FIG. 4 is a plot of hydraulic pressurethat is applied to the driveline disconnect clutch versus time. Thehydraulic pressure may be roughly indicative of driveline disconnectclutch torque capacity. The hydraulic pressure that is applied to thedriveline disconnect clutch increases in the direction of the verticalaxis arrow. The horizontal axis represents time and time increases fromthe left side of the figure to the right side of the figure. Trace 408represents the hydraulic pressure that is applied to close the drivelinedisconnect clutch (e.g., the driveline disconnect clutch pressure).

At time t0, transmission oil temperature is low and the engine is notrunning (e.g., rotating and combusting fuel). The electric machine isgenerating a small amount of electric torque and the drivelinedisconnect clutch pressure is zero so the driveline disconnect clutch isfully open. Such conditions may be present when a vehicle is stopped andthe electric machine is rotating the torque converter to maintaintransmission pump output.

At time t1, the engine is started and it begins to generate torque. Theelectric machine is switched to generator mode and it begins supplyingcharge to the electric energy storage device. In one example, thevehicle system controller initiates these actions responsive to electricenergy storage device SOC being less than a threshold. The drivelinedisconnect clutch pressure is increased so that engine torque may betransferred to the electric machine. The transmission oil temperaturebegins to rise since the transmission oil pressure is in a priority zonewhere at least some transmission oil pump flow is directed away from thetransmission lube circuit and transmission oil cooler so that the oilpressure delivered to the driveline disconnect clutch may reach adesired pressure so that the engine torque may be delivered to theelectric machine.

Between time t1 and time t2, the transmission oil temperature rises andthe engine torque is reduced in response to the torque converterimpeller speed and the transmission oil temperature. The pressure thatis applied to the driveline disconnect clutch is reduced as the enginetorque is reduced. The magnitude of the negative torque provided by theelectric machine is reduced as the engine torque is reduced so that theengine speed may be maintained.

At time t2, engine torque is reduced to a level where the transmissionoil pressure stops increasing and levels off at a temperature that isbelow threshold temperature 450. The magnitude of the negative torqueproduced via the electric machine levels off and the hydraulic pressurethat is applied to the driveline disconnect clutch is reduced to a levelthat allows engine torque to be transmitted to the electric machinewithout the driveline disconnect clutch slipping.

In this way, the oil temperature of a transmission may be controlledeven when a transmission pump lacks capacity to supply a high oil flowrate to all transmission fluid circuits. Further, engine torque iscontrolled and driveline disconnect clutch capacity is controlled sothat engine torque may rotate an electric machine and charge an electricenergy storage device without slipping the driveline disconnect clutch.

Referring now to FIG. 5, a non-limiting example transmission oil circuitdiagram is shown. Circuit 500 or other transmission oil circuitconfigurations may be included in the system of FIGS. 1 and 2. Further,actuators shown in circuit 500 may be adjusted according to the methodof FIG. 7.

Pump 283 is included in the torque converter 206 shown in FIG. 2 and itmay be rotated via engine 10 or electric machine 240. Pump 283 draws oil521 from sump 520. The oil may be pressurized by pump 283 and deliveredto driveline disconnect clutch 236 or gear clutches 211. Pump 283 drawsoil from sump via line or conduit 501. Pump supplies pressurized oil viapassage 502 to driveline disconnect pressure control valve 310. Speed ofpump 283 and a duty cycle of valve 510 may control pressure of oil inpassage 504, which may be referred to as transmission line pressure.Further, adjusting the duty cycle of valve 510 may adjust flow to lubepassage 503, which flows to transmission oil cooler 505. Oil that is notdirected from pump 283 to line 504 may be directed to line 503. Thus,line pressure in passage 504 may be controlled via adjusting a dutycycle of an electric signal that is supplied to valve 510. Valves 510,512, and 209 may be operated via transmission controller 254 shown inFIG. 2. It should be appreciated that the configuration of circuit 500is non-limiting and that it may be arranged differently for differenttransmissions.

Referring now to FIG. 6A, a plot 600 of transmission line pressureversus torque converter impeller speed to illustrate priority zones isshown. The vertical axis represents transmission line pressure andtransmission line pressure increases in the direction of the verticalaxis arrow. The horizontal axis represents torque converter impellerspeed and torque converter impeller speed increases in the direction ofthe horizontal axis arrow.

Curve 602 represents transmission line pressures when the full capacityof the transmission oil pump is supplied to the driveline disconnectclutch and/or other transmission clutches while substantially notransmission oil flow is directed to a lube circuit of the transmissionand the transmission oil cooler. Curve 604 represents transmission linepressures where transmission oil pump output capacity begins to bedirected away from the lube circuit and the transmission oil cooler meetrequested clutch capacities for the driveline disconnect clutch and/orgear clutches. The amount of oil that is directed away from thetransmission lube circuit and the transmission cooler to the drivelinedisconnect clutch increases in the direction from curve 604 to curve602.

The transmission line pressure is not operated in no operation zone 610(e.g., to the left of curve 602) and the line pressure is not in apriority zone at zone 614 (e.g., to the right of curve 604). In priorityzone 612 (e.g., to the left of curve 604 and to the right of curve 602),at least a portion of output from the transmission oil pump is directedaway from the transmission oil cooler and lube circuit to the drivelinedisconnect clutch and the gear clutches. This plot shows transmissionline pressures for conditions when the torque converter lockup clutch isunlocked. The line pressure curves for conditions when the torqueconverter lockup clutch is fully locked are similar to those shown inplot 600, but the line pressures at each torque converter impellerspeeds are reduced.

A trajectory 655 (e.g., in the direction of the arrow) shows that for agiven torque converter impeller speed, line pressure may be moved from apriority pressure where at least some pump output flow is directed fromthe transmission lube circuit and transmission oil cooler to thedriveline disconnect clutch so that a desired or requested drivelinedisconnect clutch torque capacity may be met. In particular, iftransmission line pressure is adjusted to point 650 at a particulartorque converter impeller speed to meet a desired or requested drivelinedisconnect clutch torque capacity, then the transmission line pressuremay be reduced to point 650 to reduce transmission oil temperature whilethe torque converter impeller speed is maintained. Reducing thetransmission line pressure to point 650 allows transmission oil to flowto the transmission oil cooler and lube circuit to keep transmission oiltemperature within a desired temperature range.

Referring now to FIG. 6B, an example table for limiting torque converterimpeller torque is shown. Table 670 includes a plurality of cells thatmay be referenced via torque converter impeller speed and transmissionoil temperature. The values in table 670 represent empiricallydetermined torque converter impeller maximum torque threshold levels(e.g., torque levels that are not to be exceeded). The values shown intable 670 are non-limiting and are for illustration purposes.Interpolation may be used to determine values between values that areincluded in the individual cells. In this example, vertical cells arereferenced by torque converter impeller speed and horizontal cells arereferenced by transmission oil temperature. The table indicates that athigher transmission oil temperatures, the torque converter impellertorque is limited or reduced to lower levels than for lower transmissionoil temperatures. This allows the transmission to exit the priority linepressure control region at higher transmission oil temperatures toreduce the possibility of transmission oil degradation and componentdegradation.

Referring now to FIG. 7, a flow chart of a method for operating adriveline and maintaining transmission oil temperature below a thresholdtemperature while charging a battery while a vehicle is stopped ormoving at less than a threshold speed is shown. The method of FIG. 7 maybe incorporated into and may cooperate with the system of FIGS. 1 and 2.Further, at least portions of the method of FIG. 7 may be incorporatedas executable instructions stored in non-transitory memory while otherportions of the method may be performed via a controller transformingoperating states of devices and actuators in the physical world. Method700 may be executed when a vehicle in which includes the engine andelectric machine described herein is stopped and not moving.Alternatively, method 700 may be performed when the vehicle is moving,at less than a threshold speed for example.

At 702, method 700 determines vehicle operating conditions. Vehicleoperating conditions may include but are not limited to vehicle speed,engine speed, engine temperature, electric energy storage device stateof charge (SOC), the amount of electric power being consumed by electricpower consumers of the vehicle and that are external to the vehicle,engine load, and driver demand torque or power. Method 700 proceeds to704.

At 704, method 700 estimates a driver demand power. In one example, thedriver demand power may be determined via indexing or referencing atable or function that includes a plurality of empirically determineddriver demand power levels. The table or function may be referenced viaaccelerator pedal position and vehicle speed. The table outputs thedriver demand power. Method 700 proceeds to 706.

At 706, method 700 determines requested electric energy storage devicecharging power and the amount of electric power that is being consumedby electric power consumers in the vehicle and electric power consumersthat are external to the vehicle. In one example, the requested electricenergy storage device charging power may be determined via referencing atable or function of empirically determined electric energy storagedevice charging power values via electric energy storage device SOC andelectric energy storage device temperature. The amount of electric powerthat is being consumed may be determined via the current and voltagethat is supplied to the electric power consumers. Method 700 proceeds to710.

At 708, method 700 determines and amount of electric machine power togenerate the electric power to charge the electric energy storage deviceand to supply the electric power consumers. In one example, the amountof electric machine power to generate the power to charge the electricenergy storage device and to supply electric power to the electric powerconsumers is a sum of the amount of electric power supplied to theelectric power consumers and the requested amount of electric power tocharge the electric energy storage device. Method 700 proceeds to 710.

At 710, method 700 determines a requested amount of engine power. In oneexample, the requested engine power may be determined via indexing orreferencing a table or function of empirically determined engine powervalues via the driver demand power determined at 704 and the electricmachine power to generate the electric power to charge the electricenergy storage device and to supply the electric power consumersdetermined at 708. The table or function outputs an engine power amount.Method 700 proceeds to 712.

At 712, method 700 judges if the torque converter clutch (TCC) is fullylocked. In one example, method 700 may judge that the TCC is fullylocked based on a value of a variable stored in controller memory. Inanother example, a sensor may indicate whether or not the TCC is locked.If method 700 judges that the TCC is fully locked, the answer is yes andmethod 700 proceeds to 714. Otherwise, the answer is no and method 700proceeds to 750.

At 714, method 700 determines a transmission line pressure to transferthe requested amount of engine power to the electric machine and thedriveline downstream of the driveline disconnect clutch. In one example,method 700 indexes or references a table or function of empiricallydetermined line pressure values via the requested engine torque amountplus a predetermined offset torque amount. The engine torque amount maybe determined by dividing the requested engine power amount by thepresent engine speed. The table or function output a requested linepressure and method 700 proceeds to 716.

At 716, method 700 judges if the requested line pressure puts the lubecircuit in a priority zone where at least a portion of transmission oilpump output flow is directed to the driveline disconnect clutch to meetthe requested line pressure and the TCC is locked. In one example,method 700 references a function that describes a relationship betweenline pressure and torque converter impeller speed to describe priorityand non-priority zones for operating the transmission with a lockedtorque converter (e.g., similar to FIG. 6A). If method 700 referencesthe function and determines that the requested line pressure puts thelube circuit in a priority zone, then the answer is yes and method 700proceeds to 718. Otherwise, the answer is no and method 700 proceeds to720.

At 718, method 700 limits torque converter impeller torque via limitingengine torque. Further, method 700 reduces the driveline disconnectclutch torque capacity via reducing transmission line pressure anddirecting at least a portion of the pumps flow capacity to thetransmission lube circuit and the transmission cooler, thereby improvingcooling of transmission oil. Since the line pressure was determined tobe in a priority zone where at least a portion of flow is directed fromthe lube and transmission cooler to the driveline disconnect clutch,which tends to increase transmission oil temperature, the transmissionline pressure is reduced as a function of transmission oil temperatureand torque converter impeller speed (e.g., according to a functionsimilar to the function illustrated in FIG. 6A). The reduction in linepressure reduces the torque capacity of the driveline disconnect clutch.Therefore, the engine torque is reduced to a torque that is less thanthe driveline disconnect clutch torque capacity (e.g., driveline torquecapacity minus a predetermined offset torque) as a function oftransmission oil temperature and torque converter impeller speed (e.g.,according to a function similar to the function illustrated in FIG. 6A)and the negative torque of the electric machine is reduced to a torquethat is less than engine torque so that the engine does not stall. Theamount of the reduction in line pressure is also based on the conditionof the torque converter clutch being locked, which necessitates a lowertransmission line pressure to exit the priority zone. By reducing thenegative torque of the electric machine (e.g., when the electric machineis operating in a generator mode), charging current supplied by theelectric machine to the electric energy storage device is reduced, buttransmission cooling is improved and while charging of the electricenergy storage device may continue. Method 700 proceeds to 720.

At 750, method 700 determines a transmission line pressure to transferthe requested amount of engine power to the electric machine and thedriveline downstream of the driveline disconnect clutch. In one example,method 700 indexes or references a table or function of empiricallydetermined line pressure values via the requested engine torque amountplus a predetermined offset torque amount. The engine torque amount maybe determined by dividing the requested engine power amount by thepresent engine speed. The table or function output a requested linepressure and method 700 proceeds to 752.

At 752, method 700 judges if the requested line pressure puts the lubecircuit in a priority zone where at least a portion of transmission oilpump output flow is directed to the driveline disconnect clutch to meetthe requested line pressure and the TCC is unlocked. In one example,method 700 references a function that describes a relationship betweenline pressure and torque converter impeller speed to describe priorityand non-priority zones for operating the transmission with a lockedtorque converter (e.g., similar to FIG. 6A). If method 700 referencesthe function and determines that the requested line pressure puts thelube circuit in a priority zone, then the answer is yes and method 700proceeds to 753. Otherwise, the answer is no and method 700 proceeds to720.

At 753, method 700 limits torque converter impeller torque via limitingengine torque. Further, method 700 reduces the driveline disconnectclutch torque capacity via reducing transmission line pressure anddirecting at least a portion of the pumps flow capacity to thetransmission lube circuit and the transmission cooler, thereby improvingcooling of transmission oil. Since the line pressure was determined tobe in a priority zone where at least a portion of flow is directed fromthe lube and transmission cooler to the driveline disconnect clutch,which tends to increase transmission oil temperature, the transmissionline pressure is reduced as a function of transmission oil temperatureand torque converter impeller speed (e.g., according to a functionsimilar to the function illustrated in FIG. 6A). The reduction in linepressure reduces the torque capacity of the driveline disconnect clutch.Therefore, the engine torque is reduced to a torque that is less thanthe driveline disconnect clutch torque capacity (e.g., driveline torquecapacity minus a predetermined offset torque) as a function oftransmission oil temperature and torque converter impeller speed (e.g.,according to a function similar to the function illustrated in FIG. 6A)and the negative torque of the electric machine is reduced to a torquethat is less than engine torque so that the engine does not stall. Theamount of the reduction in line pressure is also based on the conditionof the torque converter clutch being unlocked, which necessitates alower transmission line pressure to exit the priority zone. By reducingthe negative torque of the electric machine (e.g., when the electricmachine is operating in a generator mode), charging current supplied bythe electric machine to the electric energy storage device is reduced,but transmission cooling is improved and while charging of the electricenergy storage device may continue. Method 700 proceeds to 720.

At 720, method 700 judges if SOC of the electric energy storage device(e.g., 275 of FIG. 2) is greater than a threshold level. If so, theanswer is yes and method 700 proceeds to exit. Otherwise, the answer isno and method 700 proceeds to 722.

At 722, method 700 may temporarily raise the driveline disconnect clutchtorque capacity and the engine torque output along with electric machineelectric charge output so that SOC of the electric energy storage devicemay be elevated above the threshold SOC. In one example, method 700 mayincrease the driveline disconnect clutch torque capacity, engine torqueoutput, and electric machine charge output for a predetermined amount oftime before again reducing the same to lower transmission temperature.Method 700 proceeds to exit.

In this way, temperatures of a transmission may be reduced while stillcharging an electric energy storage device via an engine through adriveline disconnect clutch and an electric machine. The method mayspecifically reduce oil flow directed to increase driveline disconnectclutch torque capacity when a vehicle is stopped and charging of anelectric energy storage device is requested.

Thus, the method of FIG. 7 provides for a driveline operating method,comprising: adjusting engine torque responsive to a transmission oiltemperature and a speed of a torque converter impeller via a controller;and adjusting a transmission line pressure responsive to the enginetorque. The method further comprises adjusting a pressure supplied to adriveline disconnect clutch responsive to the engine torque. The methodincludes where the engine torque is adjusted via a torque actuator. Themethod includes where the torque actuator is an engine throttle. Themethod includes where the torque actuator is an ignition system. Themethod further comprises adjusting the transmission line pressureresponsive to an operating state of a torque converter. The methodincludes where adjusting the transmission line pressure responsive tothe operating state of the torque converter includes adjusting thetransmission line pressure to a first pressure for a first speed of thetorque converter impeller when a torque converter clutch is locked, andadjusting the transmission line pressure to a second pressure for thefirst speed of the torque converter impeller when the torque converterclutch is not locked. The method includes where the first pressure isless than the second pressure.

The method of FIG. 7 also provides for a driveline operating method,comprising: increasing torque of an engine and a driveline disconnectclutch pressure responsive to increasing an amount of charge supplied toa battery via an electric machine while a vehicle which includes theengine is stopped; adjusting engine torque responsive to the amount ofcharge supplied to the battery when a transmission oil pressure is notin a priority zone; and adjusting engine torque responsive to atransmission oil temperature and a speed of a torque converter impellerspeed when the transmission oil pressure is in the priority zone. Themethod includes where the priority zone is where a portion oftransmission pump output is directed according to a priority. The methodalso includes where the priority increases flow to the drivelinedisconnect clutch and decreases flow to a transmission oil heatexchanger. The method includes where adjusting engine torque includedecreasing engine torque. The method further comprises decreasing theamount of charge supplied to the battery when the transmission oilpressure is in the priority zone. The method further comprises adjustingthe transmission oil pressure responsive to an operating state of atorque converter. The method includes where adjusting engine torqueincludes adjusting an engine throttle position.

In another representation, the method of FIG. 7 provides for a drivelineoperating method, comprising: constraining transmission input torque toless than a threshold via adjusting torque of an engine and adjusting atorque capacity of a driveline disconnect clutch in response to a torqueconverter clutch being locked and transmission line pressure placing alube circuit in a first priority zone, the first priority zone or regionbased on a first relationship between transmission line pressure andtorque converter impeller speed for operating with a locked torqueconverter. The method further comprises constraining the transmissioninput torque to less than the threshold via adjusting torque of anengine and adjusting the torque capacity of the driveline disconnectclutch in response to a torque converter clutch being unlocked andtransmission line pressure placing a lube circuit in a second priorityzone, the second priority zone or region based on a second relationshipbetween transmission line pressure and torque converter impeller speedfor operating with an unlocked torque converter. The method furthercomprising adjusting a driveline disconnect clutch torque capacity basedon a battery state of charge.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, atleast a portion of the described actions, operations and/or functionsmay graphically represent code to be programmed into non-transitorymemory of the computer readable storage medium in the control system.The control actions may also transform the operating state of one ormore sensors or actuators in the physical world when the describedactions are carried out by executing the instructions in a systemincluding the various engine hardware components in combination with oneor more controllers.

This concludes the description. The reading of it by those skilled inthe art would bring to mind many alterations and modifications withoutdeparting from the spirit and the scope of the description. For example,single cylinder, I3, I4, I5, V6, V8, V10, and V12 engines operating innatural gas, gasoline, diesel, or alternative fuel configurations coulduse the present description to advantage.

1. A driveline operating method, comprising: adjusting engine torqueresponsive to a transmission oil temperature and a speed of a torqueconverter impeller via a controller; and adjusting a transmission linepressure responsive to the engine torque.
 2. The method of claim 1,further comprising adjusting a pressure supplied to a drivelinedisconnect clutch responsive to the engine torque.
 3. The method ofclaim 1, where the engine torque is adjusted via a torque actuator. 4.The method of claim 3, where the torque actuator is an engine throttle.5. The method of claim 3, where the torque actuator is an ignitionsystem.
 6. The method of claim 1, further comprising adjusting thetransmission line pressure responsive to an operating state of a torqueconverter.
 7. The method of claim 6, where adjusting the transmissionline pressure responsive to the operating state of the torque converterincludes adjusting the transmission line pressure to a first pressurefor a first speed of the torque converter impeller when a torqueconverter clutch is locked, and adjusting the transmission line pressureto a second pressure for the first speed of the torque converterimpeller when the torque converter clutch is not locked.
 8. The methodof claim 7, where the first pressure is less than the second pressure.9. A driveline operating method, comprising: increasing torque of anengine and a driveline disconnect clutch pressure responsive toincreasing an amount of charge supplied to a battery via an electricmachine while a vehicle which includes the engine is stopped; adjustingengine torque responsive to the amount of charge supplied to the batterywhen a transmission oil pressure is not in a priority zone; andadjusting engine torque responsive to a transmission oil temperature anda speed of a torque converter impeller speed when the transmission oilpressure is in the priority zone.
 10. The method of claim 9, where thepriority zone is where a portion of transmission pump output is directedaccording to a priority.
 11. The method of claim 10, where the priorityincreases flow to the driveline disconnect clutch and decreases flow toa transmission oil heat exchanger.
 12. The method of claim 9, whereadjusting engine torque include decreasing engine torque.
 13. The methodof claim 9, further comprising decreasing the amount of charge suppliedto the battery when the transmission oil pressure is in the priorityzone.
 14. The method of claim 9, further comprising adjusting thetransmission oil pressure responsive to an operating state of a torqueconverter.
 15. The method of claim 9, where adjusting engine torqueincludes adjusting an engine throttle position.
 16. A system,comprising: an engine; an electric machine; a driveline disconnectclutch included in a driveline and located between the engine and theelectric machine, the driveline disconnect clutch coupled to the engineand the electric machine; and a controller including executableinstructions stored in non-transitory memory to adjust a torque of theengine responsive to a transmission oil temperature and a speed of atorque converter impeller speed.
 17. The system of claim 16, furthercomprising a torque converter and a transmission.
 18. The system ofclaim 17, where the torque converter is coupled to the transmission andthe electric machine.
 19. The system of claim 16, further comprisingadditional instructions to adjust a transmission line pressureresponsive to the torque of the engine.
 20. The system of claim 16,further comprising additional instructions to adjust a pressure suppliedto a driveline disconnect clutch responsive to the torque of the engine.